U.S. patent application number 14/331393 was filed with the patent office on 2014-10-30 for method for coating devices using electrospinng and melt blowing.
The applicant listed for this patent is Cardiac Pacemakers, Inc.. Invention is credited to Devon N. Arnholt, Douglas D. Pagoria, Jeannette C. Polkinghorne.
Application Number | 20140324141 14/331393 |
Document ID | / |
Family ID | 46934665 |
Filed Date | 2014-10-30 |
United States Patent
Application |
20140324141 |
Kind Code |
A1 |
Arnholt; Devon N. ; et
al. |
October 30, 2014 |
METHOD FOR COATING DEVICES USING ELECTROSPINNG AND MELT BLOWING
Abstract
A medical electrical lead may include an insulative lead body, a
conductor disposed within the insulative lead body, an electrode
disposed on the insulative lead body and in electrical contact with
the conductor and a fibrous matrix disposed at least partially over
the electrode. The fibrous matrix may be formed from a
non-conductive polycarbonate polyurethane polymer.
Inventors: |
Arnholt; Devon N.;
(Shoreview, MN) ; Pagoria; Douglas D.; (Forest
Lake, MN) ; Polkinghorne; Jeannette C.; (Spring Lake
Park, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cardiac Pacemakers, Inc. |
St. Paul |
MN |
US |
|
|
Family ID: |
46934665 |
Appl. No.: |
14/331393 |
Filed: |
July 15, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13571553 |
Aug 10, 2012 |
|
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14331393 |
|
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61523069 |
Aug 12, 2011 |
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Current U.S.
Class: |
607/116 ;
264/465 |
Current CPC
Class: |
A61N 1/05 20130101; D10B
2331/06 20130101; D01D 5/0084 20130101; Y10T 29/49224 20150115;
D10B 2321/08 20130101; D01D 5/0023 20130101; Y10T 29/4922 20150115;
A61N 1/056 20130101 |
Class at
Publication: |
607/116 ;
264/465 |
International
Class: |
A61N 1/05 20060101
A61N001/05; D01D 5/00 20060101 D01D005/00 |
Claims
1. A medical electrical lead comprising: an insulative lead body
extending from a distal region to a proximal region; a conductor
disposed within the insulative lead body and extending from the
proximal region to the distal region; an electrode disposed on the
insulative lead body and in electrical contact with the conductor;
and a non-conductive fibrous matrix comprising polycarbonate
polyurethane disposed at least partially over the electrode, the
fibrous matrix having an average fiber diameter less than about
0.750 microns and having a thickness between 13 microns to 51
microns.
2. The medical electrical lead of claim 1, wherein the fibrous
matrix comprises electrospun polycarbonate polyurethane.
3. A method of forming a medical electrical lead having an
insulative lead body and an electrode disposed on the insulative
lead body, the method comprising steps of: forming a fibrous matrix
comprising a non-conductive polycarbonate polyurethane polymer by
electrospinning or meltblowing; and disposing the fibrous matrix at
least partially over the electrode; wherein the fibrous matrix has
an average fiber diameter less than about 0.750 microns and has a
thickness between 13 microns to 51 microns.
4. The method of claim 3, wherein forming the fibrous matrix
comprises electrospinning polycarbonate polyurethane.
5. The method of claim 4, wherein prior to electrospinning a
coating solution comprising from 3% to 40% by weight of
polycarbonate polyurethane is prepared.
6. The method of claim 3, wherein forming the fibrous matrix
comprises melt blowing polycarbonate polyurethane.
7. The method of claim 3, wherein forming the fibrous matrix
comprises forming the fibrous matrix directly onto the
electrode.
8. The method of claim 3, wherein forming the fibrous matrix
comprises forming the fibrous matrix on a substrate and depositing
the fibrous matrix at least partially over the electrode.
9. The method of claim 3, wherein the fibrous matrix has sufficient
fiber-to-fiber spacing to deliver electrophysiological therapy
through the matrix.
10. The method of claim 9, wherein the fibrous matrix has an
average fiber-to-fiber spacing between about 10 microns to about 50
microns.
11. The method of claim 10, wherein the fibrous matrix has an
average fiber-to-fiber spacing between about 10 microns to about 25
microns.
12. A medical electrical lead comprising: an insulative lead body
extending from a distal region to a proximal region; a conductor
disposed within the insulative lead body and extending from the
proximal region to the distal region; an electrode disposed on the
insulative lead body and in electrical contact with the conductor;
and a fibrous matrix comprising a non-conductive polycarbonate
polyurethane polymer disposed at least partially over the
electrode, the fibrous matrix having an average fiber diameter less
than about 0.750 microns.
13. The medical electrical lead of claim 12, wherein the fibrous
matrix has a thickness between about 2.54 microns to about 254
microns.
14. The medical electrical lead of claim 12, wherein the fibrous
matrix has sufficient fiber-to-fiber spacing to deliver
electrophysiological therapy through the matrix.
15. The medical electrical lead of claim 14, wherein the fibrous
matrix has an average fiber-to-fiber spacing between about 10
microns to about 50 microns.
16. The medical electrical lead of claim 15, wherein the fibrous
matrix has an average fiber-to-fiber spacing between about 10
microns to about 25 microns.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/571,553, entitled "METHOD FOR COATING
DEVICES USING ELECTROSPINNING AND MELT BLOWING", filed Aug. 10,
2012, which claims priority to U.S. Provisional Application Ser.
No. 61/523,069, filed Aug. 12, 2011, each of which is commonly
owned and is incorporated herein in its entirety by reference.
TECHNICAL FIELD
[0002] The present invention relates to methods for manufacturing
medical devices. More specifically, the invention relates to
methods for coating medical devices and to coated medical
devices.
BACKGROUND
[0003] Cardiac pacing leads are well known and widely employed for
carrying pulse stimulation signals to the heart from a battery
operated pacemaker, or other pulse generating means, as well as for
monitoring electrical activity of the heart from a location outside
of the body. Electrical energy is applied to the heart via an
electrode to return the heart to normal rhythm. Some factors that
affect electrode performance include polarization at the
electrode/tissue interface, electrode capacitance, sensing
impedance, and voltage threshold. In all of these applications, it
is highly desirable to optimize electrical performance
characteristics at the electrode/tissue interface.
[0004] Recognized performance challenges of materials
conventionally used as electrodes include difficulty controlling
tissue in-growth, inflammation in the vicinity of the implanted
device and/or the formation of fibrous scar tissue. These
challenges may lead to difficulty in extracting the lead and/or
reduced electrode performance over time.
SUMMARY
[0005] Disclosed herein are various embodiments of a coated medical
device, as well as methods for coating medical devices.
[0006] In Example 1, a medical electrical lead includes an
insulative lead body extending from a distal region to a proximal
region. A conductor is disposed within the insulative lead body and
extends from the proximal region to the distal region. An electrode
is disposed on the insulative lead body and is in electrical
contact with the conductor. A non-conductive fibrous matrix
including polycarbonate polyurethane is disposed at least partially
over the electrode. The fibrous matrix has an average fiber
diameter of less than or equal to about 0.750 microns and a
thickness between 13 microns and 51 microns.
[0007] In Example 2, the medical electrical lead according to
Example 1, wherein the fibrous matrix includes electrospun
polycarbonate polyurethane.
[0008] In Example 3, a medical electrical lead having an insulative
lead body and an electrode disposed on the insulative lead body is
formed by forming a fibrous matrix including a non-conductive
polymer by electrospinning or meltblowing. The fibrous matrix is
disposed at least partially over the electrode and has an average
fiber diameter of less than or equal to about 0.750 microns, and a
thickness between 13 microns and 51 microns.
[0009] In Example 4, the method according to Example 3, wherein
forming the fibrous matrix includes electrospinning polycarbonate
polyurethane.
[0010] In Example 5, the method according to Example 4, wherein
prior to electrospinning, a coating solution including from 3% to
40 wt % by weight of polycarbonate polyurethane is prepared.
[0011] In Example 6, the method according to Example 3, wherein
forming the fibrous matrix comprises melt blowing polycarbonate
polyurethane.
[0012] In Example 7, the method according to any of Examples 3 to
6, wherein forming the fibrous matrix includes forming the fibrous
matrix directly onto the electrode.
[0013] In Example 8, the method according to any of Examples 3 to
6, wherein forming the fibrous matrix comprises forming the fibrous
matrix on a substrate and depositing the fibrous matrix at least
partially over the electrode.
[0014] In Example 9, the method according to any of Examples 3 to
8, wherein the fibrous matrix has sufficient fiber-to-fiber spacing
to deliver electrophysiological therapy through the matrix.
[0015] In Example 10, the method according to Example 9, wherein
the fibrous matrix has an average fiber-to-fiber spacing between
about 10 microns and about 50 microns.
[0016] In Example 11, the method according to Example 10, wherein
the fibrous matrix has an average fiber-to-fiber spacing between
about 10 microns and about 25 microns.
[0017] In Example 12, a medical electrical lead includes an
insulative lead body extending from a distal region to a proximal
region. A conductor is disposed within the insulative lead body and
extends from the proximal region to the distal region. An electrode
is disposed on the insulative lead body and is in electrical
contact with the conductor. A fibrous matrix including a
non-conductive polycarbonate polyurethane polymer is disposed at
least partially over the electrode. The fibrous matrix has an
average fiber diameter of less than or equal to about 0.750
microns.
[0018] In Example 13, the medical electrical lead according to
Example 12, wherein the fibrous matrix has a thickness between
about 2.54 microns to about 254 microns.
[0019] In Example 14, the medical electrical lead according to any
of Examples 12 or 13, wherein the fibrous matrix has sufficient
fiber-to-fiber spacing to deliver electrophysiological therapy
through the matrix.
[0020] In Example 15, the medical electrical lead according to
Example 14, wherein the fibrous matrix has an average
fiber-to-fiber spacing between about 10 microns and about 50
microns.
[0021] In Example 16, the medical electrical lead according to
Example 15, wherein the fibrous matrix has an average
fiber-to-fiber spacing between about 10 microns and about 25
microns.
[0022] While multiple embodiments are disclosed, still other
embodiments of the present invention will become apparent to those
skilled in the art from the following detailed description, which
shows and describes illustrative embodiments of the invention.
Accordingly, the drawings and detailed description are to be
regarded as illustrative in nature and not restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic view of a medical electrical lead
according to embodiments of the present invention.
[0024] FIGS. 2A and 2B are schematic longitudinal cross-sections of
a medical electrical lead according to embodiments of the present
invention.
[0025] FIG. 3 is a schematic illustration of electrospinning.
[0026] FIG. 4 is a schematic illustration of melt blowing.
[0027] FIG. 5 is a graphical representation of experimental
data.
[0028] FIG. 6 is a graphical representation of experimental
data.
[0029] While the invention is amenable to various modifications and
alternative forms, specific embodiments have been shown by way of
example in the drawings and are described in detail below. The
intention, however, is not to limit the invention to the particular
embodiments described. On the contrary, the invention is intended
to cover all modifications, equivalents, and alternatives falling
within the scope of the invention as defined by the appended
claims.
DETAILED DESCRIPTION
[0030] FIG. 1 is a partial cross-sectional view of a medical
electrical lead 10, according to various embodiments of the present
disclosure. According to some embodiments, the medical electrical
lead 10 can be configured for implantation within a patient's
heart. According to other embodiments, the medical electrical lead
10 is configured for implantation within a patient's neurovascular
regions. In yet another embodiment, the lead 10 can be a lead for a
cochlear implant. The medical electrical lead 10 includes an
elongated, insulative lead body 12 extending from a proximal end 16
to a distal end 20. The proximal end 16 is configured to be
operatively connected to a pulse generator via a connector 24. At
least one conductor 32 extends from the connector 24 at the
proximal end 16 of the lead 10 to one or more electrodes 28 at the
distal end 20 of the lead 10. The conductor 32 can be a coiled or
cable conductor. According to some embodiments where multiple
conductors are employed, the lead can include a combination of
coiled and cable conductors. When a coiled conductor is employed,
according to some embodiments, the conductor can have either a
co-radial or a co-axial configuration.
[0031] The lead body 12 is flexible, but substantially
non-compressible along its length, and has a circular
cross-section. According to one embodiment of the present
disclosure, an outer diameter of the lead body 12 ranges from about
2 to about 15 French. In many embodiments, the lead body 12 does
not include a drug collar or plug.
[0032] The medical electrical lead 10 can be unipolar, bipolar, or
multi-polar depending upon the type of therapy to be delivered. In
embodiments of the present disclosure employing multiple electrodes
28 and multiple conductors 32, each conductor 32 is adapted to be
connected to an individual electrode 28 in a one-to-one manner
allowing each electrode 28 to be individually addressable.
Additionally, the lead body 12 can include one or more lumens
adapted to receive a guiding element such as a guidewire or a
stylet for delivery of the lead 10 to a target location within a
patient's heart.
[0033] The electrodes 28 can have any electrode configuration as is
known in the art. According to one embodiment of the present
disclosure, at least one electrode can be a ring or partial ring
electrode. According to another embodiment, at least one electrode
28 is a shocking coil. According to yet another embodiment of the
present disclosure, at least one electrode 28 includes an exposed
electrode portion and an insulated electrode portion. In some
embodiments, a combination of electrode configurations can be used.
The electrodes 28 can be coated with or formed from platinum,
stainless steel, titanium, tantalum, palladium, MP35N, other
similar conductive material, alloys of any of the foregoing
including platinum-iridium alloys, and other combinations of the
foregoing including clad metal layers or multiple metal
materials.
[0034] According to various embodiments, the lead body 12 can
include one or more fixation members for securing and stabilizing
the lead body 12 including the one or more electrodes 28 at a
target site within a patient's body. The fixation member(s) can be
active or passive. An exemplary active fixation member includes a
screw-in fixation member. Examples of passive fixation members can
include pre-formed distal portions of the lead body 12 adapted to
bear against vessel walls and/or expandable tines provided at the
distal end of the lead body 12.
[0035] The lead 10 includes a fibrous matrix that is disposed over
various parts of the insulative lead body 12. FIGS. 2A and 2B
provide illustrative but non-limiting examples of regions of the
lead 10 that may include a fibrous matrix. FIGS. 2A and 2B are
schematic longitudinal cross-sectional views of the lead 10 of FIG.
1, in which internal structure has been removed for clarity.
[0036] FIG. 2A shows a fibrous matrix 40 disposed over a portion of
the insulative lead body 12. The illustrated portion of the
insulative lead body 12 may be adjacent an electrode such as the
electrode 28, or it may be spaced apart from the electrodes. In
contrast, FIG. 2B illustrates a fibrous matrix 40 disposed over the
electrode 28. While the fibrous matrix 40 is illustrated as
covering all of the electrode 28, in some embodiments the fibrous
matrix 40 covers only a small portion of the electrode 28, a
substantial portion of the electrode 28, or an intervening fraction
of the electrode 28.
[0037] In some embodiments, the fibrous matrix 40 may provide
various beneficial functionalities to the lead 10. In some
embodiments, the fibrous matrix 40 may improve the abrasion
resistance of the lead 10. In some embodiments, the fibrous matrix
40 may improve the electrical or thermal insulation of the lead 10.
In some embodiments, the fibrous matrix 40 may provide improved
control over tissue ingrowth, particularly at the site of the
electrode 28. In certain embodiments, the amount of tissue ingrowth
may be determined by tissue extraction in which the force required
to remove an implanted lead 10 is measured with an Instron force
gauge. In some embodiments, the thickness and average fiber
diameter of fibrous matrix 40 impacts tissue ingrowth. The
thickness and average fiber diameter of fibrous matrix 40 may also
impact the ability to deliver electrophysiological therapy through
fibrous matrix 40. In certain embodiments, the fibrous matrix 40
does not significantly impact the impedance of the lead 10.
[0038] The fibrous matrix 40 includes a plurality of randomly
aligned fibers that comprise the matrix. In certain embodiments the
fibrous matrix 40 may be formed by electrospinning or melt blowing,
for example. The fibers may have diameters in the range of about
10-3000 nanometers (nm), for example. The fiber diameter size may
be about 40-2000 nm, about 50-1500 nm or about 100-1000 nm, for
example. The fiber diameter size may be measured by taking the
average size of the fibers. In certain embodiments, the fibers may
have diameters as little as 40 nm, 50 nm, 100 nm or 150 nm and as
great as 300 nm, 400 nm, 500 nm, 600 nm, 650 nm, 700 nm, 725 nm,
750 nm or 800 nm or may be within any range delimited by any pair
of the foregoing values. In other embodiments, the fibers may have
an average diameter size less than about 800 nm, 750 nm, 725 nm,
700 nm, 600 nm, 500 nm or 400 nm. In other embodiments, the fiber
matrix 40 may be formed partially or completely with hollow fibers
using modified electrospinning and meltblowing techniques.
[0039] The fibrous matrix 40 may have an average fiber-to
fiber-spacing in the range of about 1 to about 100 microns, more
particularly from about 10 to about 50 microns, even more
particularly from about 10 to about 25 microns. In some
embodiments, the fiber spacing between adjacent fibers may be
adjusted or regulated to control tissue ingrowth while minimizing
impact on pacing capability. This can be accomplished, for example,
by altering the deposition parameters or deposition material. In
other embodiments, tissue in-growth is controlled by the thickness
of the matrix. Suitable thicknesses for the fibrous matrix may
range from about 0.00254 millimeters (mm) to about 0.254 mm (about
0.0001 inches (in.) to about 0.01 in.), more particularly from
about 0.0127 mm to about 0.127 mm (about 0.0005 in. to about 0.005
in.), even more particularly from about 0.0254 mm to about 0.0762
mm (about 0.001 in. to about 0.003 in.).
[0040] In some embodiments, particularly when the fibrous matrix 40
is disposed at least partially over an electrode such as the
electrode 28, the fibrous matrix 40 may have sufficient fiber
spacing to permit ions to flow through the fibrous matrix 40 such
that electrical contact may be made with the electrode 28.
[0041] A wide range of polymers may be used to prepare the fibrous
matrix 40, including both conductive and non-conductive polymer
materials. Suitable non-conductive polymers (i.e. polymers that are
not intrinsically conductive) include homopolymers, copolymers and
terpolymers of various polysiloxanes, polyurethanes,
fluoropolymers, polyolefins, polyamides and polyesters. The
non-conductive material in certain embodiments is free or
substantially free of dopant materials that facilitate polymer
conductivity. In other embodiments, the conductive material may
comprises less than 5 weight percent (wt %) dopant, more
particularly, less than 1 wt % dopant, even more particularly less
than 0.5 wt % dopant. Suitable conductive polymers are disclosed in
U.S. Pat. No. 7,908,016, which is incorporated herein by reference
in its entirety.
[0042] In certain embodiments, the fibrous matrix 40 is formed from
a non-conductive polyurethane material. Suitable polyurethanes may
include polycarbonate, polyether, polyester and polyisobutylene
(PIB) polyurethanes. Example suitable PIB polyurethanes are
disclosed in U.S. published application 2010/0023104, which is
incorporated herein by reference in its entirety. Further examples
of such copolymers and methods for their synthesis are generally
described in WO 2008/060333, WO 2008/066914, U.S. application Ser.
No. 12/492,483 filed on Jun. 26, 2009, entitled POLYISOBUTYLENE
URETHANE, UREA AND URETHANE/UREA COPOLYMERS AND MEDICAL DEVICES
CONTAINING THE SAME, and U.S. application Ser. No. 12/874,887,
filed Sep. 2, 2010, and entitled Medical Devices Including
Polyisobutylene Based Polymers and Derivatives Thereof, all of
which are incorporated herein by reference in their entirety. In
other embodiments, the fibrous matrix 40 is formed from a
non-conductive fluoropolymer material. Suitable fluoropolymer
materials include polyvinylidene fluoride, poly(vinylidene
fluoride-co-hexafluoropropene) (PVDF HFP), polytetrafluoroethylene
and expanded polytetrafluoroethylene.
[0043] As described herein, the average diameter size of the
fibrous matrix 40 may reduce tissue ingrowth. In some embodiments,
the fibrous matrix 40 may include a polyurethane, such as a
polycarbonate polyurethane and have an average diameter size of
less than about 800 nm or less than about 750 nm. In other
embodiments, the fibrous matrix 40 may include PVDF HFP and have an
average diameter size of less than about 800 nm or less than about
730 nm.
[0044] The fibrous matrix 40 may be formed using several different
techniques, such as electrospinning and melt blowing. In some
embodiments, smaller fiber sizes may be achieved using
electrospinning. FIGS. 3 and 4 schematically illustrate both
techniques.
[0045] FIG. 3 provides a schematic illustration of electrospinning.
An electric field may be used to draw a polymer solution or melt 54
from a capillary source 52. In some embodiments, the capillary
source 52 may be a syringe. The polymer solution or melt 54 is
drawn to a grounded collector 58. A high voltage power supply 56
may be used to power the process. The elements 60 to be coated may
be placed on the collector 58 to be coated. Upon drying, a thin
polymeric web 62 may be formed. In some embodiments, the fiber
sizes may be controlled by adjusting the relative concentration of
polymer in the polymer solution or melt 54.
[0046] The concentration of polymer in the electrospinning solution
and solvent selection are important factors in achieving desired
fibrous matrix properties, and in particular for controlling
porosity and/or fiber size. Additionally, a small amount of a metal
salt solution may be added to the electrospinning solution to
improve deposition. In other embodiments, the electrospinning
solution has a polymer concentration of between about 1 wt % and
about 40 wt %, more particularly between about 1 wt % and about 30
wt %, even more particularly from about 3 wt % to about 15 wt %,
and even more particularly from about 5 wt % to about 15 wt %.
Suitable solvents include dimethylformamide, dimethylacetamide,
N-methyl-2-pyrrolidone, dimethyl sulfoxide, acetone, cyclohexane
tetrohydrofuran as well as mixtures and co-solvents thereof.
[0047] In other embodiments, the polymer may be a polyurethane
polymer and the electrospinning solution may have a polymer
concentration as little as 1%, 3% or 5%, or as great as 15%, 30% or
40% or may be within any range delimited by any pair of the
foregoing values. In certain embodiments, the polymer may be a
fluoropolymer and the electrospinning solution may have a polymer
concentration as little as 5%, 10%, 15% or 20%, or as great as 30%,
35% or 40% or may be within any range delimited by any pair of the
foregoing values.
[0048] FIG. 4 provides a schematic illustration of meltblowing. An
apparatus 70 is configured to accommodate a polymer melt 72. The
polymer melt 72 passes through an orifice 74 and is carried through
the orifice 74 via streams of hot air 76 that pass through the
apparatus 70. As the polymer melt 72 exits the orifice 74, they are
met with streams of heated air 78 that helps elongate the polymer
melt 72. As a result, the polymer melt 72 forms fibers 80 that
impinge onto a collector 82. An element to be coated may simply be
placed on or in front of the collector 82.
[0049] In some embodiments, the lead 10 may be assembled before the
fibrous matrix 40 is formed directly on the lead 10. In some
embodiments, the fibrous matrix 40 may be formed on a component of
the lead 10 before the lead 10 is assembled. In some embodiments,
the fibrous matrix 40 may be separately formed and then
subsequently disposed onto a portion of the lead 10.
[0050] In certain embodiments, the fibrous matrix may be formed
from more than one polymer material in the form of a composite or
material layers. In one example, a first layer comprising a first
polymer material may be deposited onto a portion of the lead 10,
followed by a second layer formed by a second polymer material.
Additional layers may also be applied as desired. In another
example, one of a plurality of layers comprises a non-conductive
polymer material while another of the plurality of layers comprises
a conductive material. In a further example, each layer comprises a
non-conductive material.
[0051] Although the description herein discusses the fibrous matrix
40 on a lead 40, fibrous matrix 40 may be on any medical electrical
device such as but not limited to implantable electrical
stimulation systems including neurostimulation systems such as
spinal cord stimulation (SCS) systems, deep brain stimulation (DBS)
systems, peripheral nerve stimulation (PNS) systems, gastric nerve
stimulation systems, cochlear implant systems, and retinal implant
systems, among others, and cardiac systems including implantable
cardiac rhythm management (CRM) systems, implantable
cardioverter-defibrillators (ICD's), and cardiac resynchronization
and defibrillation (CRDT) devices, among others.
EXPERIMENTAL SECTION
Impedance Testing
Comparative Samples A and B and Samples C-F
[0052] A group of coil pacing lead electrodes were tested for
resistance over a series of 20 shocks at pulse intervals of 10
seconds. Comparative Samples A and B were pacemaker leads including
commercially available electrodes produced with a tissue growth
inhibition process. Samples C-F were formed from the same type of
lead as Samples A and B but the electrodes were coated with a
fibrous matrix of Tecothane 55D, commercially available polyether
polyurethane, deposited on the electrode by electrospinning. To
form the fibrous matrix, a coating solution containing 5 wt %
Tecothane in dimethylacetamide was prepared. The coating solution
was loaded into a single needle electrospinning apparatus
approximately 10 centimeters (cm) from the electrode surface. The
electrospinning apparatus was used to deposit the fibrous matrix
onto the electrode under ambient conditions to form a coating
thickness of approximately 0.051 mm (0.002 in.).
[0053] FIG. 5 provides a graphical representation of the impedance
testing. While Comparative Sample A and Sample B provide the lowest
resistance and least variability, Samples C-F exhibited comparable
resistance near 45 ohms over the course of the 20 pulses. This
indicates that the fibrous matrix did not substantially increase
the impedance of the electrode.
Comparative Sample G and Samples H-J
[0054] A group of coil pacing lead electrodes were tested for
resistance over a series of 20 shocks at pulse intervals of 10
seconds. Comparative Sample G was a pacemaker lead including a
commercially available electrode produced with a tissue growth
inhibition process. Samples H, I and J were formed from the same
type of lead as Comparative Sample G, but the electrodes were
covered with a fibrous matrix of poly(vinylidene
fluoride-co-hexafluoropropene)(PVDF H FP), a commercially available
fluoropolymer including poly(vinylidene fluoride, deposited on the
electrode by electrospinning. To form the fibrous matrix, a coating
solution containing 25 wt % PVDF HFP in dimethylformamide was
prepared. The coating solution was loaded into a single needle
electrospinning apparatus approximately 10 centimeters from the
electrode surface. The electrospinning apparatus was used to
deposit the fibrous matrix onto the electrode under ambient
conditions. Six leads were covered for each Sample with fibrous
matrix thicknesses ranging from 0.018 mm to 0.051 mm (0.0007 in. to
0.002 inches). The samples were then treated with a poly(ethylene
glycol) dimethacrylate solution to increase wettability.
[0055] FIG. 6 provides a graphical representation of the impedance
testing. While Sample G provided the lowest resistance and least
variability, Samples H-J exhibited comparable resistance over the
course of the 20 pulses. This indicates that the fibrous matrix did
not substantially increase the impedance of the electrode.
Tissue Extraction
[0056] A shocking coil was implanted subcutaneously into patient
tissue. Thirty days after implantation, an incision was made at one
end of the shocking coil. The end of the coil was excised out of
the tissue and attached to an Instron force gauge. The maximum
force to completely extract the coil from under the skin
longitudinally was recorded. A greater the extraction force
indicates a greater degree of tissue adhesion or tissue ingrowth.
In some embodiments, a suitable product may have an extraction
force less than or about equivalent to a currently commercially
available product.
Samples K and L and Comparative Samples M and N
[0057] A group of shocking coils were tested for tissue extraction
and tissue adhesion. Sample K included a polycarbonate urethane
fibrous matrix, having an average fiber size of about 0.3 microns
and Sample L included a polycarbonate urethane fibrous matrix
having an average fiber size of about 0.750 microns. The fibrous
matrixes of Samples K and L were formed by electrospinning and had
a thicknesses ranging from 0.013 millimeters (mm) to 0.051 mm
(0.0005 inches (in) to 0.002 in). Comparative Sample M and
Comparative Sample N were commercially available coils produced by
different tissue growth inhibition processes. The tissue extraction
results in newtons (N) are provided in Table 1.
TABLE-US-00001 TABLE 1 Comparative Comparative Sample K Sample L
Sample M Sample N Average Max 2.61 4.68 1.49 3.75 force (N)
Standard 0.166 0.098 0.335 0.362 Deviation
[0058] As shown in Table 1, a fibrous matrix having an average
diameter of 0.3 microns (Sample K) required less force to extract
than a fibrous matrix having an average diameter of about 0.750
microns (Sample L), illustrating that the extraction force required
decreases with reduced fiber diameters. Further, Sample K required
a slightly greater extraction force than commercially available
coil Sample M and less force to extract than commercially available
coil Sample N. Sample L required more force to extract than Sample
M and Sample N. In some embodiments it may be desirable that the
extraction force required for the fibrous matrix coated coil to be
less than or equal to that of commercially available coils, such as
Comparative Sample M and Comparative Sample N.
[0059] Samples O and P and Comparative Samples Q and R
[0060] The amount of force required to extract coils having a
fibrous matrix including PVDF HFP were also investigated. Samples 0
and P included a PVDF HFP fibrous matrix having an average fiber
diameter of about 0.730 microns. The fibrous matrixes of Samples 0
and P were formed by electrospinning and had a thickness ranging
from 0.013 mm to 0.051 mm (0.0005 in to 0.002 in). Comparative
Sample Q and Comparative Sample R were commercially available coils
produced with different tissue growth inhibition processes. The
tissue extraction results in newtons (N) are presented in Table
2.
TABLE-US-00002 TABLE 2 Comparative Comparative Sample O Sample P
Sample Q Sample R Average 6.79 7.84 2.36 4.60 Max force (N)
Standard 0.222 0.546 0.334 0.459 Deviation
[0061] As shown in Table 2, fibrous matrixes containing PVDF HFP
and having an average fiber size of about 0.730 microns required a
larger force for extraction than Comparative Sample Q and
Comparative Sample R. Sample O and Sample P suggest that PVDF HFP
fibers having an average fiber diameter greater than about 0.730
microns may require undesirably high extraction forces.
[0062] Various modifications and additions can be made to the
exemplary embodiments discussed without departing from the scope of
the present invention. For example, while the embodiments described
herein refer to particular features, the scope of this invention
also includes embodiments having different combinations of features
and embodiments that do not include all of the described features.
Accordingly, the scope of the present invention is intended to
embrace all such alternatives, modifications, and variations as
fall within the scope of the claims, together with all equivalents
thereof.
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